This book is about an investigation on compatibility of pesticides that are used commonly in agriculture as well as horticulture farms with entomopathogenic fungi. It also puts a focus on pathogenicity of the entomopathogenic fungi sample that has been found compatible against pesticides with cow pea aphid under controlled condition. It can guide farmers and allied personnel's about whether the pesticides and entomopathogenic fungi could express themselves at their highest or produce a synergistic or antagonistic pattern. The present investigations were also a part of authors post-graduate studies.